Control units for activating occupant protection means in a vehicle known from the related art are characterized, among other things, in that all supply voltages which are required for operating the occupant protection system are generated within the occupant protection system itself In this way, it is possible to ensure that correct functionality is provided, independently of fluctuations of the battery voltage in the vehicle. The voltage regulators used may be designed as linear regulators and/or DC/DC converters, for example, and may provide fixedly predefined output voltages, such as 6.7 V, 5.0 V, 3.3 V, for directly supplying other system components, such as microcontrollers, sensors, communication interfaces, lamp drivers and the like.
The output voltages of the extra-low voltage regulators (5.0 V and 3.3 V) may be monitored by a system ASIC (application-specific integrated circuit) itself, an enabling or triggering of a reset signal being derivable from the monitoring of the output voltages. The reset signal may, in turn, be used to enable or to activate, or to reset, the occupant protection system, i.e., to transfer it into a safe state in which the occupant protection system provides no functionality. Thus, to provide the full functionality of the occupant protection system, the monitored voltages must be available and within the allowed range. However, there is no option in present occupant protection systems for deactivating the voltage regulators or for suspending the monitoring of the output signals of the voltage regulators. It is thus always necessary for all voltage regulators to be connected to correct external components, so that the regulated voltages are stable and their monitoring functions robustly. This is also necessary if the output voltage of one regulator, such as 5.0 V, in the specific occupant protection system is not even used due to customer requirements. It is also possible that not all voltage regulators are required in occupant protection systems in which multiple system ASICs are combined; nonetheless, all existing voltage regulators must be correctly connected to prevent the occupant protection system from remaining in the reset state. Comparable, freely available system ASICs for occupant protection systems also offer no option of deactivating individual integrated regulators if these are monitored and used to generate the reset signal.
The German Published Patent Application No. 10 2009 047 480 A1, for example, describes a control unit and a method for activating occupant protection means for a vehicle. The described control unit includes a supply module, which converts an input voltage for the activation of the occupant protection means. A voltage regulator, which limits the input voltage to a predefined first value, is connected between a vehicle supply voltage and the input voltage of the supply module. A shutoff circuit, which shuts off the voltage regulator as a function of the vehicle supply voltage, is connected upstream from the voltage regulator, the shutoff circuit checking the vehicle supply voltage against a second value and shutting off the voltage regulator if this second value is exceeded.